Device for injecting a mono-propellant with a large amount of flow rate modulation

ABSTRACT

The device for injecting a liquid mono-propellant with a large amount of modulation of its flow rate and disposed at an upstream end of the wall of a combustion chamber of a rocket engine has a feed channel for feeding a mono-propellant from a tank. The device includes a single annular speed-up channel connected to the feed channel and having its outlet opening out via an annular injection section, the speed-up channel and the annular injection section being defined firstly by a first wall forming a stationary surface of revolution situated level with said upstream end, and secondly by a second wall forming a surface of revolution that is on a part that is movable in translation relative to the first wall forming a stationary surface of revolution.

FIELD OF THE INVENTION

The present invention relates to a device for injecting a liquidmono-propellant with a large amount of flow rate modulation and with itbeing possible to shut the injection plane for extinction andre-ignition purposes, the device being located at an upstream end of thewall of a combustion chamber of a rocket engine and including a feedchannel for feeding a mono-propellant from a tank.

PRIOR ART

Various liquid propellant injector devices for rocket engines arealready known.

By way of example, FIG. 5 shows a “pintle” type device that makes itpossible, for bi-propellant injection, to modulate the flow rate to alarge extent as a result of the injection sections being varied by amovable part 34.

In the system of FIG. 5, an oxidizer is injected into the combustionchamber 30 through an annular orifice 32 between a movable part 34 and astationary part 36 coaxially located therein. A fuel is also injectedthrough an annular orifice 38 around the movable part 34, between themovable part and a portion of the wall of the combustion chamber 30. Thefuel and the oxidizer diverge away from their respective outlet orificesand form jets that meet and mix in an annular combustion zone designatedby reference 40.

Nevertheless, implementing two independent feed systems for a fuel andfor an oxidizer makes fabrication rather complex and the device cannotbe compact, in particular when it incorporates a shutter rod.

In general, a bi-propellant design with two sheets that are to mixtogether in part by friction on meeting each other in a zone of acombustion chamber does not enable optimum atomization to be achieved,in particular during an ignition stage.

U.S. Pat. No. 3,742,701 describes an injector device for injecting aliquid bi-propellant that is to react with a solid propellant. Themovable part of that injector device flares downstream and is verysensitive to the pressure that exists in the combustion chamber withwhich the injector device is associated.

DEFINITION AND OBJECT OF THE INVENTION

The present invention seeks to remedy the above-mentioned drawbacks andto enable a compact injector device to be provided that is adapted tomono-propellant injection, presenting a design that is simplified andthat enables the injection flow rate to be modulated while providingimproved atomization, together with closure in a single zone (in theinjection plane).

These objects are achieved, in accordance with the invention, by adevice for injecting a liquid mono-propellant with a large amount offlow rate modulation, the device being disposed at the upstream end of awall of a combustion chamber of a rocket engine and including a channelfor feeding it with a mono-propellant from a tank, wherein the devicehas a single annular speed-up channel connected to the feed channel andhaving its outlet opening out via an annular injection section, thespeed-up channel and the annular injection section being defined firstlyby a first wall forming a stationary surface of revolution situatedlevel with said upstream end, and secondly by a second wall forming asurface of revolution on a part that is movable in translation relativeto said first wall forming a stationary surface of revolution andpresenting beside the combustion chamber a free end that constitutes afine point.

Preferably, the device has a third wall forming a stationary surface ofrevolution situated facing the annular injection section to receive ajet of the liquid mono-propellant projected through the annularinjection section.

In a first possible embodiment, the third wall constituting a stationarysurface of revolution is formed on a central endpiece connected to theupstream end of the wall of the combustion chamber.

In a second possible embodiment, the third wall constituting astationary surface of revolution is formed on a peripheral ringconnected to the upstream end of the wall of the combustion chamber.

According to an advantageous characteristic of the invention, themovable part has a pilot section that is subjected to the effects of thefluid flow rate in the feed channel and that acts against the action ofa resilient element dimensioned to enable the movable part to move intoan open position when a predetermined force is exerted on the pilotsection.

Nevertheless, in another possible embodiment, the movable part iscoupled to an actuator to be moved under force control.

The technology of the invention is based on associating a system formodulating the flow rate of a mono-propellant with the propellant beingatomized in a free sheet or by impacting against a stationary wall,possibly also in association with a shutter.

When a resilient element is used, it may be constituted by a calibratedspring or by a set of spring washers.

In a first embodiment, the first wall constituting a stationary surfaceof revolution and the second wall constituting a surface of revolutionon the movable part are frustoconical with their small bases facingtowards the third wall constituting a stationary surface of revolution.

In a second embodiment, the first wall constituting a stationary surfaceof revolution and the second wall forming a surface of revolution on themovable part are frustoconical with their large bases facing towards thethird wall constituting a stationary surface of revolution.

Advantageously, the third wall constituting a stationary surface ofrevolution is frustoconical.

According to a particular characteristic of the present invention, themono-propellant feed holes are defined by a bell-shaped body having: abearing flange fastened by bolts to the upstream end of the combustionchamber wall; a guide surface for the movable part; and also a sealingsurface against which a gasket slides.

The design of the body for fabrication in a singleconcentricity-imparting stage makes it possible to ensure that the sheetis regular around its entire periphery and that closure is practicallyperfect;

In a second embodiment, the device may include a central part secured tosaid central column that defines the first wall constituting astationary surface of revolution and that further includes a front wallwith a portion situated facing the third wall constituting a stationarysurface of revolution, which portion forms a reflector for the jet ofliquid mono-propellant projected against the third wall constituting astationary surface of revolution.

In an advantageous aspect of the present invention, the resilientelement is constituted by a spring against which a bearing ring bears,having a position that is adjusted by screws for adjusting intranslation the tension of the spring that determines the openingcondition for the injector.

In another advantageous aspect of the present invention, it furthercomprises a sensor for sensing movement in translation of the movablepart that serves to determine by simple geometrical calculation the flowsection through the speed-up channel.

In general, for a mono-propellant, the invention enables the injectionflow rate to be modulated using a small flow rate on ignition andsubsequently a large amount of variation by having an injection sectionthat is variable while enabling the speed of injection to be relativelystable.

Injection may be closed off completely in the injection plane when themono-propellant flow rate is zero, thereby avoiding any combustion inthe cavities of the injector, any combustion residues, or indeed anyexplosions, given the nature of certain propellants.

The system is mechanically simple and very compact, having only a singlepropellant feed channel.

Atomization takes place by the propellant being projected against astationary wall, thereby providing atomization that is better than thatprovided by an impact between two sheets.

Furthermore, the injector device is easily adaptable and the centralendpiece used as a projection or reflection surface may be easilyinterchangeable in order to adapt the shape or the angle of thestationary surface that receives the impact of a propellant jet. Undercertain conditions of injection and fluid state, the endpiece may beomitted so as to operate with atomization in a free sheet.

The device of the invention is applicable to any rocket enginepresenting a high degree of thrust modulation (using liquid or hybridpropellant), and the invention also relates to a rocket engine fittedwith the liquid mono-propellant injector device.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention can bebetter understood on reading the following description of particularembodiments, given by way of non-limiting indication, and with referenceto the drawings, in which:

FIG. 1 is a diagrammatic axial section view of a mono-propellantinjector device in a first embodiment of the invention, having a centralendpiece;

FIG. 2 is a diagrammatic axial section view of a variant embodiment ofthe FIG. 1 injector device, which device is combined with a device forcontrolling shutting of the throat of the combustion chamber;

FIG. 3 is a diagrammatic axial section view of a mono-propellantinjector device in a second embodiment of the invention, with astationary peripheral wall for receiving the impact of the jet ofpropellant;

FIG. 4 is a diagrammatic axial section view of a variant embodiment ofthe FIG. 3 injector device, with a device for adjusting the tension of aspring in translation and a sensor for sensing the movement intranslation of the movable part that modulates the propellant flow rate;

FIG. 5 is a diagrammatic axial section view of a prior art device forbi-propellant injection that is provided with a movable part formodulating the rate at which one propellant is injected;

FIG. 6 is a diagrammatic axial section view of a variant embodiment ofthe FIG. 1 injector device; and

FIG. 7 is a diagrammatic axial section view of a variant embodiment ofthe FIG. 3 injector device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to FIG. 1, there can be seen a diagrammatic longitudinalsection view of a first element of a mono-propellant injector device ofthe invention.

FIG. 1 shows a portion of a combustion chamber 9 defined by a wall 90having a front end identified by reference 91.

A bell-shaped body 1 has a flange-shaped base that is fastened on theend wall 91 by fastener elements 92 such as bolts. The body 1 definesliquid propellant feed holes 6 that are side by side around the ring andin communication with a tank through a space defined by a second body 11fastened to the bell-shaped body 1 by bolts or screws 12.

An endpiece 2 secured to the bell-shaped body 1 is disposed in thecombustion chamber 9 and presents a stationary surface of revolution 21,e.g. a frustoconical surface, that is situated facing and at a shortdistance away from a propellant injection section 3 that is incommunication via an annular speed-up segment 4 with the injection feedholes 6.

A movable part 5 forms a body of revolution arranged coaxially with thebody 1 and guided relative thereto by means of a guide surface 52providing long guidance. The movable part 5 has a head portion 7 ofgreater diameter that defines a surface for receiving a gasket 51 thatprovides sealing relative to the body 1.

A face 71 of the head portion 7 of the movable part 5 defines a pilotsection that is subjected to the variations in the flow rate of thepropellant flowing through the feed holes 6, with these flow ratevariations varying in substantially the same manner as pressure.

The rear face of the head portion 7 of the movable part 5 is subjectedto the action of a resilient element such as a spring 8 that isinterposed between the stationary body 1 and the movable part 5.

The spring 8 is dimensioned in such a manner as to urge the movableportion 5 into its position for closing the propellant injection section3 in an outlet plane of the injector when the flow rate of themono-propellant is zero, and to cause said propellant injection section3 to open when the flow rate of propellant acting on the pilot section71 produces a predetermined effect on the spring 8.

Adjacent to the endpiece 2, the movable part 5 has a terminal portion 95that is frustoconical in shape and co-operates with a stationary wall 94that is likewise frustoconical and is formed by a portion of the endwall 91 that projects into the chamber 9 so as to define a speed-upchannel 4 that opens out into the combustion chamber 9 via the injectionsection 3 situated facing the frustoconical wall of the endpiece 2.

At the outlet from the injector, the liquid mono-propellant is atomizedon striking the wall 21 of the endpiece 2.

The frustoconical walls 94, 95 (first and second walls) defining thespeed-up channel 4 have their small bases directed towards the endpiece2. In the example shown in FIG. 1, the frustoconical wall 21 (thirdwall) of the endpiece 2 has its small base closest to the injectionsection 3, but the stationary wall 21 could present some otherconfiguration adapted to the nature of the propellant and/or operatingconditions. The endpiece 2 defining the projection surface 21 isremovable, and confers modularity, enabling the shape and the angle ofinclination of the projection surface 21 to be adapted as a function ofthe type of impact that is desired.

The injector device of the invention adapted to a mono-propellant has asingle speed-up channel 4 and serves to atomize the propellant byprojecting it against a stationary wall 21, thereby contributing todefine a device with improved compactness and capacity for atomizing.

The mechanical architecture is capable of guaranteeing a very highdegree of precision in manufacture and of conferring excellentreliability on the injector device.

The bell-shaped body 1 with a central guide column may be machined in asingle stage (see the variant embodiment of FIG. 2). Given thestatically-indeterminate nature of the system, this concept makes itpossible to guarantee good concentricity so as to achievesimultaneously:

-   -   long guidance of the movable part 5 along the surface 52;    -   sealing relative to the outside surface of the movable part 5        via the gasket 51; and    -   centering of the body 1 via its plane engagement on the end        plate 91 of the wall 90 of the combustion chamber 9, the end        plate defining via its projecting portion the stationary wall 94        that co-operates with the movable wall 95 of the movable part 5        to define the speed-up channel 4. The facts of minimizing the        number of parts that are stacked on one another and of machining        long cylinders in a single stage serves to guarantee good        operation, in particular concerning the uniformity of the        injected sheet and contact between surfaces when shut.

Furthermore, beside the combustion chamber 9, the movable part 5 isterminated by a free end in the form of a fine point so as to minimizethe effects of pressure in the chamber 9 on the spring 8, or on thespring washers that could be used instead of the spring 8.

FIG. 2 shows a variant embodiment of the FIG. 1 injector device adaptedto circumstances in which a central rod 13A is axially movable underdrive from a spring 14 and may serve, for example, to control selectiveshutting of the throat of the combustion chamber 9. Under suchcircumstances, the bell-shaped body 1 itself includes, formed integrallywith the body 1, a central tubular portion that is interposed betweenthe movable part 5 and the central rod 13A so as to providesimultaneously long guidance for the movable part 5 and short centeringfor the movable central rod 13 relative to the stationary body 1. Themovable central rod 13A is provided with other short centering situatedupstream from the throat of the combustion chamber 9.

The operation of the FIG. 2 variant is otherwise analogous to that ofthe FIG. 1 embodiment and the description of elements that they have incommon, which elements are given the same references, is not repeated.

FIG. 2 shows a protective coating 93 on the inside face of thecombustion chamber wall 90, which coating could also be applied in theother embodiments that are described.

FIGS. 3 and 4 show a second embodiment of the invention that relies onthe same principles as the first embodiment of FIGS. 1 and 2, but inwhich the stationary wall receiving the impacts from the mono-propellantjets is not formed on a central endpiece, but instead is formed by aprojecting portion 120 of the end wall 191 of the wall 190 defining thecombustion chamber 109.

The mono-propellant jets coming from the injection section 103 andspeeded up in a speed-up channel 104 are not projected in convergingmanner as in the embodiment of FIGS. 1 and 2, but in diverging manner soas to strike the peripheral wall 121 where they are atomized.

As in the first embodiment, a bell-shaped body 101 has a base supportedon the end wall 191 and fastened thereto by fastener means 192.

The body 101 has a central tubular portion 111 that serves firstly tohold a central tubular part defining a central channel 106 for feeding amono-propellant, and secondly serves as a sealing surface for a gasket151 mounted on the movable part 105 having its terminal portionco-operating with a stationary centering part 130 to define the annularspeed-up channel 104 and the annular outlet section 103 for the liquidmono-propellant. The gasket 151 also acts as a damper to avoidoscillation.

The central tubular part defining the central channel 106 for feedingthe mono-propellant may be fastened to the body 101 by a nut 112.

The movable part 105 is guided by the inside surface 113 of the bell andpresents a pilot section 171 that is subjected to the variations in theflow rate of the mono-propellant in the annular portion 107 of the feedchannel 106.

A spring 108 is interposed between the movable part 105 and a topportion of the body 101 to keep the outlet section 103 shut when thepropellant flow rate is zero, and to cause said section to open when apredetermined force is exerted by the flow rate of the mono-propellanton the pilot surface 171.

The stationary centering part 130 has a stationary frustoconicalperipheral wall 195 situated facing a frustoconical terminal wall 194 ofthe movable part 105 to define the speed-up channel 104. The large basesof the frustoconical portions face towards the stationary wall 121 suchthat the propellant jets diverge.

After being injected through the outlet section 103 and atomized byimpacting against the stationary wall 121, projections of propellant maybe present on the front peripheral wall 131 of the stationary centeringpart 130.

The atomized droplets initially formed by the propellant impactingagainst the stationary peripheral frustoconical wall 121 are redirectedtowards the center on being reflected by the front peripheral wall 131.

As in the first embodiment, injecting the mono-propellant at a flow ratethat is modulatable and with a speed of injection that is stable givesrise to the propellant being atomized by impacting against a stationarywall while using a mechanical system that is simple and compact.

The bell-shaped body 101 with a column 111 in the center may be machinedin a single stage. Given the statically-indeterminate nature of thesystem, proceeding in this manner makes it possible to guarantee goodconcentricity so as to ensure simultaneously long guidance for themovable part 105 via the outside surface thereof, sealing with thegasket 151 relative to the inside surface of the movable part 105, andshort centering with a plane bearing surface for the body 101 againstthe end plate 191 of the chamber so as to ensure that the impact surface121 is properly centered.

The facts of minimizing the number of parts that are stacked one onanother, and of machining long cylinders in a single stage serves toguarantee regularity for the injected sheet and for contact betweensurfaces on closure.

As in the first embodiment, the tip of the movable part 105 constitutesa fine point to minimize the effects of pressure in the chamber 109 onthe spring 108 or on spring washers that could be used instead of thespring 108.

FIG. 4 shows a variant embodiment in which a ring 170 is placed on thespring 108 and is kept pressed against the spring 108 by screws 173(e.g. six screws disposed at 60° intervals from one another). Thisenables the tension of the spring 108 to be adjusted by being moved intranslation via the ring 170. This tension determines the condition foropening the injector. Tests and adjustments may be performed usingwater, for example.

Optionally, a movement sensor 172 for sensing movement in translationacts on the rear portion of the movable part 105 that is subjected tothe action of the spring 108, thereby making it possible by simplegeometrical calculation to determine the flow section in the speed-upchannel 104. This provides a regulated system that controls injectionspeed as well as possible.

The adjustment and regulation elements 170, 171, and 172 may also beimplemented with the first embodiment of FIGS. 1 and 2 so as to act onthe spring 8 and the movable part 5.

Under certain conditions of fluid state and injection, the projectingportion 20; 120 with the surface 21; 121 may be omitted for operationtaking place with atomization in a free sheet.

Furthermore, and optionally, the pilot section 71; 171 and the spring 8;108 can be omitted. In these variations of the embodiments of FIGS. 1and 3, as shown in FIGS. 6 and 7 respectively, the movable part 5; 105is coupled to an actuator 81; 181 that may, by way of example, be of themechanical, hydraulic, or electrical type so as to be controlled interms of force. In the drawings, there can be seen essentially theactuator control rods that are engaged in orifices formed in the body 1;101.

In the variant of FIG. 7, the nut 112 may be omitted and the parts 101and 130 may be secured to each other by welding, thereby releasing spaceto receive the actuator 181. Under such circumstances, propellant feedmay take place not via a central channel 106 but via a torus feeding allof the bores formed in the part 101, as in the variant embodiment ofFIG. 6.

In the present description, and in conventional manner, a member is saidto be for “short centering” when it defines a zone of contact that canbe modelled as a sphere-cylinder contact.

If the length of the contact zone is L and if the diameter of the shortcentering member is D, then a relationship of the following typeapplies:L≦0.8D

Preferably, it is possible to choose the value for the length L of thecontact zone to lie within the following range of values:0.1D≦L≦0.5D

In more preferred manner, it is possible to select the value for thelength L of the contact zone to lie in the following range of values:0.1D≦L≦0.3D

Furthermore, likewise in conventional manner, a member is said to be for“long centering” when it defines a contact zone that can be modelled asa pivoting-sliding contact.

If the length of the contact zone is L and if the diameter for themember for long centering is D, then a relationship of the followingtype applies:D≦L

Preferably, a value may be selected for the length L of the contact zonethat lies in the following range of values:1.5D≦L

What is claimed is:
 1. A device for injecting a liquid mono-propellantwith a large amount of flow rate modulation, the device being disposedat the upstream end of a wall of a combustion chamber of a rocket engineand including a channel for feeding it with a mono-propellant from atank, wherein the device has a single annular speed-up channel connectedto the feed channel and having its outlet opening out via an annularinjection section, the speed-up channel and the annular injectionsection being defined firstly by a first wall forming a stationarysurface of revolution situated level with said upstream end, andsecondly by a second wall forming a surface of revolution on a part thatis movable in translation relative to said first wall forming astationary surface of revolution and presenting beside the combustionchamber a free end that constitutes a fine edge, and wherein the movablepart has a pilot section that is subjected to the effects of the fluidflow rate in the feed channel and that acts against the action of aresilient mechanical element dimensioned to enable the movable part tomove into an open position when a predetermined force is exerted on thepilot section.
 2. A device according to claim 1, having a third wallforming a stationary surface of revolution situated facing the annularinjection section to receive a jet of the liquid mono-propellantprojected through the annular injection section.
 3. A device accordingto claim 2, wherein the third wall constituting a stationary surface ofrevolution is formed on a central endpiece connected to the upstream endof the wall of the combustion chamber.
 4. A device according to claim 2,wherein the third wall constituting a stationary surface of revolutionis formed on a peripheral ring connected to the upstream end of the wallof the combustion chamber.
 5. A device according to claim 1, wherein theresilient element is constituted by a calibrated spring or by a set ofspring washers.
 6. A device according to claim 1, wherein the first wallconstituting a stationary surface of revolution and the second wallconstituting a surface of revolution on the movable part arefrustoconical with their small bases facing towards the third wallconstituting a stationary surface of revolution, which third wall isformed on a central endpiece connected to the upstream end of the wallof the combustion chamber.
 7. A device according to claim 1, wherein thefirst wall constituting a stationary surface of revolution and thesecond wall forming a surface of revolution on the movable part arefrustoconical with their large bases facing towards the third wallconstituting a stationary surface of revolution, which third wall isformed on a peripheral ring connected to the upstream end of the wall ofthe combustion chamber.
 8. A device according to claim 2, wherein thethird wall constituting a stationary surface of revolution isfrustoconical.
 9. A device according to claim 1, wherein themono-propellant feed holes are defined by a bell-shaped body having: abearing flange fastened by bolts to the upstream end of the combustionchamber wall; and a guide surface for the movable part; and also asealing surface against which a gasket slides.
 10. A device according toclaim 9, including a central part secured to a central column thatdefines the first wall constituting a stationary surface of revolutionand that further includes a front wall with a portion situated facingthe third wall constituting a stationary surface of revolution, whichportion forms a reflector for the jet of liquid mono-propellantprojected against the third wall constituting a stationary surface ofrevolution, which third wall is formed on a peripheral ring connected tothe upstream end of the wall of the combustion chamber.
 11. A deviceaccording to claim 1, wherein the resilient element is constituted by aspring against which a bearing ring bears, having a position that isadjusted by screws for adjusting in translation the tension of thespring that determines the opening condition for the injector.
 12. Adevice according to claim 1, further comprising a sensor for sensingmovement in translation of the movable part that serves to determine bysimple geometrical calculation the flow section through the speed-upchannel.
 13. A device according to claim 1, wherein the part that ismovable in translation is coupled to an actuator.
 14. A device accordingto claim 10, wherein the external diameter of the movable part issubstantially equal to the maximum external diameter of said stationarycentral part at the level of said fine edge.